PARIS (AFP) - A group of 25 extremists is planning to return to Europe after combat training in the Afghan-Pakistani border regions, French intelligence officials said on Wednesday, citing a US tip-off. The warning came at a time of high alert for possible attacks in European countries following warnings by several countries. A group of 25 young people trained in combat after travelling from their homes in Europe to the region, considered a hotbed of violent extremism, plan to head back again possibly via Turkey, one intelligence source told AFP. The source said US intelligence services alerted their counterparts in Europe to the groups activities a few weeks ago and the warning was reiterated by British authorities. One French official said the group of 25 has experience of fighting in the lawless border region and could be able to organise other extremists in Europe. These people are the main worry of Western security services, said one official. On Tuesday French police arrested 12 people and seized guns in anti-terror raids. Police from Frances anti-terrorism squad made nine arrests in the southern port of Marseille and in nearby Avignon. On Wednesday they named one of the suspects as Fouad Sabour, 45, known to police as an extremist linked to previous attacks. In a separate operation Tuesday, French police arrested three men after finding their numbers in the mobile phone of Ryad Hannouni, a 28-year-old of Algerian origin, who was picked up Saturday in the Italian city of Naples allegedly carrying a bomb-making kit. Officials said investigators wanted to question him on suspected links to militants coming to Europe from Afghanistan. Hannouni had reportedly travelled from tribal zones around the Afghan-Pakistan border. Police said the three arrested in the second French raid were not themselves being held on terrorism charges and had suspected links with organised crime.